Thin-film transistors (TFTs) pervade our daily lives as indispensable elements in a myriad of electronic/photonic products, such as computers, cell phones, displays, household appliances and sensors. Furthermore, the future demand for next-generation mobile computing, communication and identification devices is expected to increase markedly. For diverse multiple functionalities, the electronics of ideal mobile devices must achieve light weight, low power consumption, low operating voltages (powered by household batteries) and compatibility with diverse substrates. Additional desirable features include optical transparency (‘invisible electronics’), mechanical ruggedness, environmental stability and inexpensive room-temperature/large-area fabrication.
TFTs meeting all the aforementioned requirements have proved elusive and will doubtless require a new direction in choice of materials and processing strategies. Conventional inorganic TFTs based on silicon and related semiconductors exhibit desirable features, such as high carrier mobilities, but are also limited by marginal mechanical flexibility and/or mandatory high-temperature processing (frequently >400° C. for II/VI and III/V compound semiconductors and >250° C. for Si TFTs). While amorphous silicon TFTs have been fabricated on flexible plastic substrates at temperatures as low as 75-150° C., reported carrier mobilities are modest (˜0.03-1 cm2V−1s−1 on inorganic insulators) and the material is optically opaque. Organic semiconductor materials provide low temperature processability and are compatible with substrate flexibility, but have typically provided low field-effect mobilities. Likewise, various concerns persist relating to choice of dielectric material and corresponding fabrication technique, such concerns as can relate to choice and incorporation of any one particular semiconductor material. Such complexities and competing issues illustrate an on-going concern in the art. The search continues for a comprehensive approach to TFT fabrication, one available at low process temperatures and/or compatible with flexible plastic substrates.